<select class="combox" name="authType" width="200">
    <option value="MD5" th:selected="${entity.authType}=='MD5'">MD5</option>
    <option value="RSA" th:selected="${entity.authType}=='RSA'">RSA</option>
    <option value="AES" th:selected="${entity.authType}=='AES'">AES</option>
</select>